1Kernel driver NCT6775
2=====================
3
4.. note::
5
6    This driver supersedes the NCT6775F and NCT6776F support in the W83627EHF
7    driver.
8
9Supported chips:
10
11  * Nuvoton NCT6102D/NCT6104D/NCT6106D
12
13    Prefix: 'nct6106'
14
15    Addresses scanned: ISA address retrieved from Super I/O registers
16
17    Datasheet: Available from the Nuvoton web site
18
19  * Nuvoton NCT5572D/NCT6771F/NCT6772F/NCT6775F/W83677HG-I
20
21    Prefix: 'nct6775'
22
23    Addresses scanned: ISA address retrieved from Super I/O registers
24
25    Datasheet: Available from Nuvoton upon request
26
27  * Nuvoton NCT5573D/NCT5577D/NCT6776D/NCT6776F
28
29    Prefix: 'nct6776'
30
31    Addresses scanned: ISA address retrieved from Super I/O registers
32
33    Datasheet: Available from Nuvoton upon request
34
35  * Nuvoton NCT5532D/NCT6779D
36
37    Prefix: 'nct6779'
38
39    Addresses scanned: ISA address retrieved from Super I/O registers
40
41    Datasheet: Available from Nuvoton upon request
42
43  * Nuvoton NCT6791D
44
45    Prefix: 'nct6791'
46
47    Addresses scanned: ISA address retrieved from Super I/O registers
48
49    Datasheet: Available from Nuvoton upon request
50
51  * Nuvoton NCT6792D
52
53    Prefix: 'nct6792'
54
55    Addresses scanned: ISA address retrieved from Super I/O registers
56
57    Datasheet: Available from Nuvoton upon request
58
59  * Nuvoton NCT6793D
60
61    Prefix: 'nct6793'
62
63    Addresses scanned: ISA address retrieved from Super I/O registers
64
65    Datasheet: Available from Nuvoton upon request
66
67  * Nuvoton NCT6795D
68
69    Prefix: 'nct6795'
70
71    Addresses scanned: ISA address retrieved from Super I/O registers
72
73    Datasheet: Available from Nuvoton upon request
74
75  * Nuvoton NCT6796D
76
77    Prefix: 'nct6796'
78
79    Addresses scanned: ISA address retrieved from Super I/O registers
80
81    Datasheet: Available from Nuvoton upon request
82
83
84
85Authors:
86
87	Guenter Roeck <linux@roeck-us.net>
88
89Description
90-----------
91
92This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
93and compatible super I/O chips.
94
95The chips support up to 25 temperature monitoring sources. Up to 6 of those are
96direct temperature sensor inputs, the others are special sources such as PECI,
97PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
98can be monitored and compared against minimum, maximum, and critical
99temperatures. The driver reports up to 10 of the temperatures to the user.
100There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
101one VID, alarms with beep warnings (control unimplemented), and some automatic
102fan regulation strategies (plus manual fan control mode).
103
104The temperature sensor sources on all chips are configurable. The configured
105source for each of the temperature sensors is provided in tempX_label.
106
107Temperatures are measured in degrees Celsius and measurement resolution is
108either 1 degC or 0.5 degC, depending on the temperature source and
109configuration. An alarm is triggered when the temperature gets higher than
110the high limit; it stays on until the temperature falls below the hysteresis
111value. Alarms are only supported for temp1 to temp6, depending on the chip type.
112
113Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
114triggered if the rotation speed has dropped below a programmable limit. On
115NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
11616, 32, 64 or 128) to give the readings more range or accuracy; the other chips
117do not have a fan speed divider. The driver sets the most suitable fan divisor
118itself; specifically, it increases the divider value each time a fan speed
119reading returns an invalid value, and it reduces it if the fan speed reading
120is lower than optimal. Some fans might not be present because they share pins
121with other functions.
122
123Voltage sensors (also known as IN sensors) report their values in millivolts.
124An alarm is triggered if the voltage has crossed a programmable minimum
125or maximum limit.
126
127The driver supports automatic fan control mode known as Thermal Cruise.
128In this mode, the chip attempts to keep the measured temperature in a
129predefined temperature range. If the temperature goes out of range, fan
130is driven slower/faster to reach the predefined range again.
131
132The mode works for fan1-fan5.
133
134sysfs attributes
135----------------
136
137pwm[1-7]
138    - this file stores PWM duty cycle or DC value (fan speed) in range:
139
140	   0 (lowest speed) to 255 (full)
141
142pwm[1-7]_enable
143    - this file controls mode of fan/temperature control:
144
145	* 0 Fan control disabled (fans set to maximum speed)
146	* 1 Manual mode, write to pwm[0-5] any value 0-255
147	* 2 "Thermal Cruise" mode
148	* 3 "Fan Speed Cruise" mode
149	* 4 "Smart Fan III" mode (NCT6775F only)
150	* 5 "Smart Fan IV" mode
151
152pwm[1-7]_mode
153    - controls if output is PWM or DC level
154
155	* 0 DC output
156	* 1 PWM output
157
158Common fan control attributes
159-----------------------------
160
161pwm[1-7]_temp_sel
162			Temperature source. Value is temperature sensor index.
163			For example, select '1' for temp1_input.
164
165pwm[1-7]_weight_temp_sel
166			Secondary temperature source. Value is temperature
167			sensor index. For example, select '1' for temp1_input.
168			Set to 0 to disable secondary temperature control.
169
170If secondary temperature functionality is enabled, it is controlled with the
171following attributes.
172
173pwm[1-7]_weight_duty_step
174			Duty step size.
175
176pwm[1-7]_weight_temp_step
177			Temperature step size. With each step over
178			temp_step_base, the value of weight_duty_step is added
179			to the current pwm value.
180
181pwm[1-7]_weight_temp_step_base
182			Temperature at which secondary temperature control kicks
183			in.
184
185pwm[1-7]_weight_temp_step_tol
186			Temperature step tolerance.
187
188Thermal Cruise mode (2)
189-----------------------
190
191If the temperature is in the range defined by:
192
193pwm[1-7]_target_temp
194			Target temperature, unit millidegree Celsius
195			(range 0 - 127000)
196
197pwm[1-7]_temp_tolerance
198			Target temperature tolerance, unit millidegree Celsius
199
200There are no changes to fan speed. Once the temperature leaves the interval, fan
201speed increases (if temperature is higher that desired) or decreases (if
202temperature is lower than desired), using the following limits and time
203intervals.
204
205pwm[1-7]_start
206			fan pwm start value (range 1 - 255), to start fan
207			when the temperature is above defined range.
208
209pwm[1-7]_floor
210			lowest fan pwm (range 0 - 255) if temperature is below
211			the defined range. If set to 0, the fan is expected to
212			stop if the temperature is below the defined range.
213
214pwm[1-7]_step_up_time
215			milliseconds before fan speed is increased
216
217pwm[1-7]_step_down_time
218			milliseconds before fan speed is decreased
219
220pwm[1-7]_stop_time
221			how many milliseconds must elapse to switch
222			corresponding fan off (when the temperature was below
223			defined range).
224
225Speed Cruise mode (3)
226---------------------
227
228This modes tries to keep the fan speed constant.
229
230fan[1-7]_target
231			Target fan speed
232
233fan[1-7]_tolerance
234			Target speed tolerance
235
236
237Untested; use at your own risk.
238
239Smart Fan IV mode (5)
240---------------------
241
242This mode offers multiple slopes to control the fan speed. The slopes can be
243controlled by setting the pwm and temperature attributes. When the temperature
244rises, the chip will calculate the DC/PWM output based on the current slope.
245There are up to seven data points depending on the chip type. Subsequent data
246points should be set to higher temperatures and higher pwm values to achieve
247higher fan speeds with increasing temperature. The last data point reflects
248critical temperature mode, in which the fans should run at full speed.
249
250pwm[1-7]_auto_point[1-7]_pwm
251			pwm value to be set if temperature reaches matching
252			temperature range.
253
254pwm[1-7]_auto_point[1-7]_temp
255			Temperature over which the matching pwm is enabled.
256
257pwm[1-7]_temp_tolerance
258			Temperature tolerance, unit millidegree Celsius
259
260pwm[1-7]_crit_temp_tolerance
261			Temperature tolerance for critical temperature,
262			unit millidegree Celsius
263
264pwm[1-7]_step_up_time
265			milliseconds before fan speed is increased
266
267pwm[1-7]_step_down_time
268			milliseconds before fan speed is decreased
269
270Usage Notes
271-----------
272
273On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
274connected to anything and floats, or that it is connected to some non-standard
275temperature measurement device. As a result, the temperature reported on CPUTIN
276will not reflect a usable value. It often reports unreasonably high
277temperatures, and in some cases the reported temperature declines if the actual
278temperature increases (similar to the raw PECI temperature value - see PECI
279specification for details). CPUTIN should therefore be be ignored on ASUS
280boards. The CPU temperature on ASUS boards is reported from PECI 0.
281